Are people missing the fact that this guy was intentionally screwing with you?
It seems pretty clear that he didn't like the way you were driving, and decided to "teach you a lesson."
Now, without commenting on whether the lesson was deserved, or on how it was delivered, the simple fact is - he wanted to piss you off, and obviously he did.
I did about the same thing once, to some complete jackass who was tailgating me so close that I couldn't see his windshield in my rear view- only the grill of his truck. I'm going like 60 in a 45, and he flys up behind me like he's going to run me off the road. This was not cool behavior - I'm just chilling on the way home, got my shades on, listening to some music... and some ahole in a truck just about hits me - and I'm speeding! ...
Wow, did I ever piss him off - I decided to slow to a dead even pace with the old lady in the lane next to me. (who surprisingly was going exactly the speed limit) He'd swerve behind her, I'd just barely speed up - until my rear bumper was even with her front.. then he'd swerve behind me and I'd just barrreeeely slow down. Then after a mile or so, I figured ok, no big deal, maybe he's got a good reason to be in a hurry, so I'll let him go around.. the ahole decides to swerve in front of me and slam on his brakes, slows down to about 5 mph on a 45 mph road - the old lady almost turned me into a nissan sandwich. Then he gets up to me at a light and starts yelling obscenities... I don't know wtf I was thinking... I rolled my window down and looked at him and said "oh.. sorry... I thought those big POS trucks were fast enough to pass?" ... that REALLY pissed him off, light turned green and I booked - now I'm probably doing 80 and this guy is piiiiissed. He and his 2 redneck buddies in the cab decide to to try to chase me down and kill me ... (well, I presume - I ditched them about 5 miles later in a McDonalds parking lot)
Lesson learned, big rednecks in big pos trucks do not have a sense of humor, and just because you're 17 with a car that doesn't mean you're indestructable.
But don't worry, I've mellowed out a lot in the last 10 years. The irony is, most of the time I'm doing at least 15 over the limit, sometimes more like 30, so I see no reason why anybody should be passing me. But now it's the rice boys (I was stuck at a light the other night behind some moron kids who jumped out of the car (the light was green) and were draping a tee shirt over their license plate?!) and the generally clueless that have me frustrated... but I think I've found a better solution to road rage. Apparently $300 will get you a real train air horn. I bet I could have made the kids with the tee shirt wet themselves. ;-)